The present invention relates to a nozzle and, more particularly, to a fire fighting nozzle.
Typical combination fire fighting nozzles (nozzles that produce a stream that can be transitioned from a protective fog pattern to a straight stream pattern) use a stem that has a small diameter shaft attached to a larger diameter stem head. The stem head is positioned internal to the tubular tip of the nozzle such that the difference between the outside (OD) of the stem head and the inside diameter (ID) of the tip create an orifice which appropriately meters the water flow for the desired flow/pressure operational characteristics. Due to the fact that the stem heads are relatively large, the void area just beyond the nozzle orifice where the water exits the nozzle creates a natural vacuum. This vacuum helps to bring the stream together and create the “straight stream” pattern. However, this vacuum creates a negative pressure which acts against the desired directional flow of the water—the direction consistent with the effective reach of the stream.